Use .add() for sets not .append()

Fix a problem with adding patches to the 'unapplied_patches' set.

1 files changed, 1 insertions, 1 deletions

diff --git a/git-bz b/git-bz
index 935d7e1..416ced2 100755
--- a/git-bz
+++ b/git-bz
@@ -1470,7 +1470,7 @@ def filter_patches(bug, applied_commits):
             newly_applied_patches[patch] = applied_subjects[patch.description]
             seen_subjects.add(patch)
         else:
-            unapplied_patches.append(patch)
+            unapplied_patches.add(patch)
 
     return newly_applied_patches, obsoleted_patches, unapplied_patches